A fun way to spend time. Think Cluedo, but on a train and with real people!
Joonas Ollila commented
I think they've been playing this game also such that you can kill your target by putting salt in his drink (poison) or shooting with a water pistol. The water pistol part might be a bit messy on the train though :)
Antti Virolainen commented
A murder game on a train could also be a variation of the classic Assassin game ( http://en.wikipedia.org/wiki/Assassin_%28game%29 ). Briefly explained, the idea could be that all participants are put randomly to "circle of death", which means that everyone gets a piece of paper that has his or her target's name on it. Then each player tries to "murder" the target (for example) by drawing a cross to his back when no one else is watching. After a successful murder, the murderer gets the paper from the victim and can go after the next target. The game can last for several days, as it can be tricky to find situations where you are alone with your victim. (and the participants may also get little scary and try to avoid being alone with some one.) So in a way it can also promote to socialize on the train and stick to larger groups, but it also is a lot of fun (at least until you die... :)
Anna Af Hällström commented
Think Agatha Christie, think teamwork, think hidden clues, think Crimson Room, think totally awesome!